The research presented in this thesis evaluates different materials that are candidates to be used as a flexible skin on a morphing wing. A morphing wing has come to be known as any wing that changes shape. Although there has been a great amount of research involved in designing morphing mechanisms, the information for applicable wing skin material has been limited. A morphing wing skin needs to be flexible enough to deflect and morph to a new shape given a suitable amount of force, yet strong enough to resist the aerodynamic forces encountered during flight. It also must remain elastic throughout its use so there is no change in surface area which could produce unwanted air flow characteristics. A candidate material must also have excellent fatigue characteristics as well as provide environmental and chemical resistance, and withstand abrasion (e.g. rain) as conventional materials do.

This research was conducted alongside a project that developed an unmanned aerial vehicle (UAV) that utilizes wing morphing for control. The problems encountered during testing were the motivations for this study. A significant problem is the onset of material separation from the wing support structure, or ballooning, caused by the low pressure on the top surface of the wing. A bulge test facility was designed and constructed to investigate this effect and to help predict its onset. The fatigue characteristics are observed by cyclically pressurizing the material to see any change in center deflection.

A sample of rubber materials, a plastic material, a thermoplastic elastomer (TPE), polyurethane, and a woven material were evaluated. The rubber materials along with a combination of rubber and woven material were found to be the best candidates. They provided a healthy balance of flexibility and strength which is required by a flexible wing skin. A method for determining the onset of material deflection due to the surface pressure on a wing was also developed using the bulge test. Using this method one can approximately predict when and how much a material will deflect according to pressure coefficient, velocity, and altitude. Although abrasion, chemical, and environmental resistance is important it was not tested in this research.